Overdiagnosis Could Be Behind Jump In Thyroid Cancer Cases

The thyroid gland, shown in pink, plays a big role in regulating the body's metabolism.

Spencer Sutton
/ Science Source

Originally published on March 5, 2014 2:05 pm

You go in for a checkup. The doctor feels your throat. Hmm, she says, there's a lump in your thyroid gland. We better check that out.

And that might be the start of a painful, costly and unnecessary treatment for thyroid cancer, a study says.

The number of people diagnosed with thyroid cancer has tripled since 1975, but many of those cases are probably due to small, slow-growing tumors that would never cause problems, the researchers say.

"We're in the midst of an epidemic here, but it's largely an epidemic of our own creating," says Dr. Gilbert Welch, a professor of medicine at Dartmouth's Geisel School of Medicine and an author of the study. "People need to know that there's a tremendous amount of overdiagnosing going on in thyroid cancer."

Welch and his colleagues started looking at thyroid cancer back in 2006. They found that the number of cases had doubled from 1973 to 2002, but the number of people dying from the disease hadn't changed at all. If the diagnoses were catching new dangerous cancers, that death rate should have dropped.

In this latest analysis, the number of people diagnosed has accelerated, tripling from 1975 to 2009. But death rates haven't changed, remaining at 0.5 per 100,000. The study was published Thursday in JAMA Otolaryngology­ – Head and Neck Surgery.

Almost all of the increase was due to papillary thyroid cancer, a common but slow-growing form, and in tumors that were 2 centimeters or smaller.

Women appear to be especially vulnerable to overdiagnosis, the study found. The absolute increase in thyroid cancer diagnoses in women was four times higher than in men, even though men are more likely to be found having thyroid cancer in autopsies.

Treatment for thyroid cancer usually involves taking out some or all of the thyroid gland. But the voice box and nerves can be damaged during surgery, affecting the voice. So can the parathyroid gland, which controls calcium levels in the body. Once the thyroid gland is removed, people have to take thyroid replacement medication for the rest of their lives.

The manual throat exam included in physicals isn't a very good way to check a small bumpy gland, Welch says.

"A lot of us, and I include myself in this, aren't that confident about our physical exam skills," Welch told Shots. "It's easy to say that the next step is to get a more definitive test. 'Well, I don't know, maybe that's something.' Then they send you for an ultrasound."

If the ultrasound finds a nodule on the thyroid, doctors often recommend a biopsy with a very thin needle. But the results can be inconclusive, Welch says.

He studies cancer diagnosis, and focuses on how early testing and aggressive treatments affect health.

Perhaps the most useful thing for patients to know is if a nodule is growing, Welch says. "This is a basic principle that the lung cancer screeners have learned," he says. "Growth is a pretty important part of lung cancer screening for small lesions that look like cancer. We're not going to stick needles in them until they show some growth."

Since thyroid cancer screening appears to be leading to a lot more diagnoses and surgery, with no improvement in lives saved, Welch wonders if doctors should be palpating people's necks at all.

"That's not to say that people who notice a big lump on their necks shouldn't go in to see their doctors," Welch says. "That makes a lot of sense. But if people are found to have nodules that are concerning, I'd hope in the future we'll see more of a watchful waiting, active surveillance to see if that thing is growing."

Welch says medical care can do a lot for people who are sick and suffering. "But we have to ask to what extent do we want the health care system looking for things in well people," he says. "We do know that the harder we look at people, the more abnormalities we find. By the time we're middle-aged, the chances are better than not I can find something wrong with you."